Feasibility study into Onslow scheme: phase 2

Viability studies of a battery project at Lake Onslow have been moved to private property and catching up with the local community is planned.

The $4 billion project is still in the research phase and information is expected to go to cabinet by the end of the year.

A first phase of fieldwork in Teviot Valley began in June. This fieldwork took place on public land, such as road reserves, at two main sites and was completed this month.

The first work was to explore where water could be stored on the Clutha River before being pumped through a tunnel to Lake Onslow. Depending on the location, this may involve the construction of a lower reservoir.

A lower reservoir would allow the pumped hydropower system to take in and return water and minimize any effects on the river.

The feasibility study had identified three potential areas for a lower reservoir: one at Lake Roxburgh, where the lake would act as a reservoir, and two locations further downstream.

More information was needed to determine the most appropriate location, size and design for a lower reservoir, should the plan go ahead. Landowners who may be affected by the planned reservoir will be contacted.

A second phase of geotechnical work was set to begin at the end of this month at a new site on private land in the Teviot Valley. This work is an extension of the fieldwork in the Teviot Valley.

This site was selected for its near-surface-level geological features, which provide insight that can inform the broader design work of the proposed pumped water system.

This second phase of the fieldwork is expected to take approximately four weeks.

After the site work was completed, the boreholes were capped and the area was rehabilitated. In some locations, groundwater levels and pressures were monitored remotely. At these sites, a small, fenced-in structure enclosed the covered boreholes and a 5-meter pole with solar panels and data logging equipment was installed.

Once the work is complete and the site has been restored, a small area around the covered borehole will be fenced off. A small solar panel, surveillance equipment and telecommunications equipment has been installed so that groundwater data can be collected and monitored remotely. Over time, any areas where the ground has been disturbed will be restored, leaving little to no traces of activity.

A community walk-in event was planned for October 29, and it would be an opportunity to hear more about the project and talk more with members of the project team.

It was revealed last month that there was sufficient elevated water storage for the project’s upper reservoir and that the surrounding land was strong enough to support the construction of a dam. Transmission lines were large enough near the site to transmit power.

The Clutha River was also sufficiently lower in elevation than Lake Onslow with enough water to pump out and had suitable tunnel and lower inlet options.

Staff reporter

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